1. Field of the Invention
The present invention is in the field of shipping containers. More particularly, the present invention relates to shipping containers which are insulated in order to maintain an article shipped in such containers at a refrigerated temperature for several days while the container and its contents are in shipment. Still more particularly, the present invention relates to such containers which are formed at least in part of foamed polymer material.
2. Related Technology
Conventional insulated shipping containers of the so-called box-within-a-box configuration are well known. These conventional box-within-a-box containers have an outer box formed of corrugated cardboard and a smaller inner open-topped box also formed of corrugated cardboard. These two boxes define a void space therebetween, which during manufacture of such shipping containers is filled with a foamed-in-place foamed polymer material. The favored polymer material for this use is light to medium density foamed polyurethane material.
During the manufacture of such box-within-a-box containers, the inner box is supported on a manufacturing fixture having a upstanding plug member over which the inner box is closely received in inverted position. Next, the outer box is inverted onto this manufacturing fixture with its top closure flaps turned outward, and its bottom closure flaps opened. The manufacturing fixture includes an outer movable wall structure which supports the side walls of the outer box. The polymer material in a liquid pre-foamed condition is sprayed into the void space between the two boxes, and foams in place. The foaming of this polymer material takes a sufficient interval of time that the bottom closure flaps of the box may be closed before the foam fills the void space, and a lid is closed over these closure flaps to support the box against the internal pressure created by the foaming polymer. As this polymer material foams in place, it bonds to both the inner and outer boxes and exerts a considerable pressure against both the inner and outer boxes. Were it not for the support to these boxes provided by the manufacturing fixture, the boxes would be seriously distorted or destroyed by the foam pressure. After an additional time interval (total time of a minute or less) the foam hardens sufficiently that the substantially finished shipping container may be removed from the fixture.
In the use of such conventional shipping containers, it is common to insert the article or articles to be shipped into the inner box along with a piece of dry ice and some loose-pack material, such as styrofoam peanuts, and to insert a form-filling cut piece of comparatively thick closed-cell foam sheet at the opening of the inner box. This closed-cell foam serves as a thermal insulator and prevents the infusion of warm ambient air or loss of chilled air from within the inner box, while also allowing the escape of carbon dioxide resulting from deliquescing of the dry ice. Next, the top closure flaps of the outer box are closed and taped, and the shipping container is ready from shipment with the attachment of a shipping label.
Unfortunately, this conventional insulated shipping container has several shortcomings. First, this conventional container is both labor and materials intensive to make. More seriously, the materials of this conventional container are not recyclable because the foamed polymer material bonds securely to the inner and outer cardboard boxes. Because these dissimilar materials are bonded together so securely that they can not be conveniently separated, most recycling facilities will not accept these containers. One suggestion for recycling these containers has been to use them as part of the fuel to an incinerator. However, the polyurethane polymer material represent air pollution concerns when so incinerated.
This shortcoming of the conventional insulated shipping containers is a serious concern with more and more states and countries requiring that shipping materials which have their destinations within their jurisdictions be recyclable, or be subject to a penalty taxation or fee for special disposal.
One suggestion which has been proposed to allow the separation of foamed polymer material and cardboard boxes of the conventional insulated shipping containers has been to simply bunch a flat sheet of plastic film within the outer box and over the inner box before the foam polymer material in a liquid form is injected. However, such an expedient results in the sheet plastic material forming folds and fissures in the excess sheet material. These folds and fissures too often form airflow pathways through which refrigerated air can escape from the container, and through which warm ambient air can enter. Also, the thickness of insulative foamed polymer material which is sometimes provided around the chamber of such insulated containers is uncontrolled and unreliable. As a result, some containers made by use of this expedient show areas where the insulating foam is too thin, and where in effect the refrigerated contents are exposed to "hot spots" of ambient heat leaking into the container. Because such insulated containers are frequently used to ship medical specimens or materials which are irreplaceable or critical to the health or life of a person, and which could be damaged or destroyed by a hot spot in the insulation around these materials in shipment, the risk is too great for such an unreliability container to be used.
In view of the deficiencies of the related technology, it is recognized as desirable to provide an insulate shipping container which is more time-efficient and material-efficient to make than the conventional insulated shipping container.
Another desirable feature for such an new insulated shipping container is for it to be totally recyclable.